Electric-arc furnace.



PATENTED AUG. 30, 1904.

A. H. IMBERT. ELECTRIC ARC FURNACE.

APPLIUATION FILED MAR. 3. 1904.

2 BHEETSBHEBT 1.

H0 MODEL.

PATENTED AUG. 30, 1904. A. H. IMBERT. ELECTRIC ARC FURNACE. urmouxon FILED MAB. a. 1904.

2 SHEETS-SHEET 2.

.NO MODEL.

mm a? Patented August 30, 1904;.

UNIT D STATES PATENT OFFICE.

ANTOINE HENRT IMBERT, OF GRAND-MONTROUGE, FRANCE, ASSIGNOR TO 'SOOIETE DE METALLURGIE ELEOTRO-THERMIQUE, OF PARIS,

FRANCE.

ELECTRIC-ARC FU RNACE.

SPECIFICATION forming part of Letters Patent No. 768,995, dated August 30, 1904.

Application filed. March 3, 1904. Serial No. 196,405. (No model.)

To aZZ whom, it natty concern:

Be it known that I, ANTOINE HENRI IMBERT, engineer, a citizen of the French Republic, residing at 75 Avenue de la Rpublique, Grand-Montrouge, Department of the Seine, France, have invented new and useful Improvements in Electric Arc Furnaces, of which the following is a specification.

My invention relates to electric furnaces exclusively heated by radiation in which the electrodes are never in contact with the materials under treatment, generally ores from which metals are to be extracted. Furnaces of this kind are already known in which the furnace-chamber is confined between a sole or hearth, a ceiling, and two side walls, the two open ends of the chamber being connected to inclined charging fines or channels.

The objects of my invention are to improve such furnaces by simplifying and improving their construction so as to prolong their life, facilitate the handling and control, also to obtain a more certain and regular working with an increased output.

The accompanying drawings show a furnace built according to my invention.

Figure 1 is a longitudinal vertical section along the line Y Y of Fig. 2. Fig. 2 is a plan view, partly in section, along the line Z Z of Fig. 1.

The furnace A is carried on a properly-arranged support B. K

The furnace-chamber a is confined between the hearth b, the ceiling c, and the two vertical side walls (Z (Z. The chamber a is connected at its two open ends with a pair of inclined charging-channels constituting prolongations of the chamber a, which become narrower at the charging ends.

f is the false sole, preferably of limestone, of the two channels 6 e.

b is the flat sole, preferably of sand, of the chamber a.

it h are the inclined soles proper, preferably of refractory plates, of the channels 6 e.

The electrodes 1' 2 c i are placed above the flat sole 5 and enter into the furnace through Openings in the side walls (Z (Z.

1' fare serpentine tubes, preferably of drawn steel, through which during the working of the furnace streams of cold water are driven in order to preserve the shape of the openings.

The ceiling c of the chamber a is formed of two archesan internal arch 0, made of plumbago bricks, and an external arch 0 of firebricks. They are built so as to leave an airspace 0 between them. The ceiling 7c of the channels 0 e is also formed of two arches, the internal arch 7r being made of fire-bricks and the external arch of ordinary bricks, with an air-space 70 between them. The gases and vapors produced in the chamber a rise through the channels 0 e and escape by the chimneys Z Z, fitted with throttle-valves m m and supported by the bases 11. a. The openings at the ends of the charging-channels may be opened and closed by counter-weighted doors 0 0.

p p are the charging-shelves.

The tapping-hole q, level with the sole 6, is for running off the molten materials or metals. The supplementary tapping-hole situated at a higher level, is for running off the slag.

A dam 8, made of plumbago, located at the junction of the part it of the ceiling with the chimney-base, is fitted with a steel tube s, through which a stream of cold water is driven to prevent deformation of the arches.

Experience has shown that in order to attain a proper utilization of the heat of the arcs it is necessary that the ceiling of the furnace should be as close as possible to the sole that is, as near as the diameter of the electrodes and the avoidance of short circuits will permit. Under such conditions no arch made of refractory materials will resist, except carbon under the form of graphite. The internal arch c is consequently made of this material. On the other hand, however, the incandescent carbon would burn if exposed to the air and would also give rise to great loss of heat on account of its great conductibility if it were not properly protected. It is therefore indispensable to build a second arch c at a given distance above the graphite arch 0, so as to form an intermediate cushion c" of Inert ber, the electrodes of the arcs, and the charging-channels. The said combination is characterized by the shape, the dimensions, and relative situations of the various parts composing the whole, as will be clearly seen from what follows. First, the length of the charging-channels should be as great as possible in order to utilize the heat radiated directly over a maximum heating-surface and to recuperate a large portion of the heat carried off by the gases and vapors issuing from the furnace-chamben and rising through the channels in an opposite direction to that of the advance of the layer of the charge of materials. The angle of the slope of the channels should be such in each particular case that according to the density and the shapegranular, ovoid, brick shape, &c.of the charge, the materials to be treated slide along the sole as the portions nearest to the arcs melt, so as to produce continuous and uniform advance of the layer of materials charged into the mouth of the furnace. Secondly, my combination has two voltaic arcs produced between the points of horizontal electrodes arranged similarly to the carbons of electric-arc-lighting lamps. These two arcs are situated near the two open ends of the furnace-chamber in such a manner that about one half of the rays emitted by each arc and of the heat emitted by the incandescent electrodes strike directly the walls of the corresponding charging-channel and the layer of materials under treatment which it contains, while the other half heat the furnace-chamber proper comprised between the two arcs. The length of said chamber or, in other words, the distance between the arcs depends, on the one hand, on the strength of the electric current employed, on the other, on the nature of the materials treated. In any case this length should be such that the central part of the chamber farthest from the electrodes be maintained sufficiently hot, so that the molten materials which accumulate on the sole remain at a proper temperature.

I have already stated that the height of the furnace-chamber should be as small as is possible without giving rise to short circuits.

It is well known to those skilled in the art that carbon is an electrical conductor and also that current of a given voltage requires a certain gap for insulation. For this reason the electrodes must not be brought so close to the ceiling of the chamber that the gap will not be sufficient to insulate the arc; otherwise arcs will be struck between the electrodes and the ceiling, and so will short-circuit and destroy the arc between the electrodes. This tendency to Short-circuiting of the are limits the degree to which the sole and ceiling of the chamber may approach each other, and for best results they should be brought as close together as the conditions will permit.

It will be observed that the chimneys are situated at the extremities of the chargingchannels, that the chimney-bases protect the top of these latter from being cooled, and that the chimneys are fitted with throttle-valves, which serve, among other purposes, to allow of the maintenance inside the furnace of a pressure slightly above that of the atmosphere, so as to prevent air penetrating therein cooling and burning the electrodes and other carbon parts or acting unfavorably on the materials under treatment.

The devices for automatically advancing the electrodes and supplying them with the current, as also those for cooling the parts outside the furnace, are not shown on the drawings. They may be of any convenient system.

The cooling serpentine tubes 7' j are only for protecting the openings in the furnacewalls through which the electrodes pass, so as to prevent any deformation of that part of the walls.

The object of the dams has already been explained.

Without limiting myself to the precise construction and arrangement of parts shown, I claim" 1. In an electric furnace, the combination with a sole or hearth, a ceiling and vertical side walls forming a chamber, of symmetrical, oppositely-inclined charging-channels connected to the chamber at its ends, and a pair of horizontal electrodes for each channel penetrating into the furnace through the side walls of the chamber and adjacent to the channel-openings, substantially as described.

2. An electric-arc furnace comprising a chamber having a sole or hearth, and a ceiling formed of an inside wall of graphitic carbon and an outside wall of refractory material,

IOU

said inside and outside walls inclosing bewith Walls inclosing a chamber, of electrodes mounted therein, inclined charging-channels communicating with said chamber at their inner ends, masonry structures inclosing the upper ends of said channels, and chimneys supported by said structures, said chimneys being in communication with said channels, substantially as described.

5. In an electric furnace, the combination With Walls inclosing a chamber, of electrodes therein, the ceiling of said chamber comprising an inside Wall of fire-brick and an outside Wall of ordinary brick, said Walls inclosing a space Which is cut off from external communication, substantially as described.

6. In an electric furnace, the combination With Walls inclosing a chamber, of electrodes ANTOINE HENRI IMBERT.

itnesses:

JUDA D. STUNoD, (JLAUDIUs LUNORE. 

